In cable operated equipment particularly grapple yarders, the operator must become extremely skilled to properly and rapidly manipulate the grapple or working element to engage and move the logs or the like.
There are three main varieties of the basic grapple yarder type equipment. Each variation incorporates a main crane structure and a grapple suspended by cables between the main crane structure and a back spar. Each also includes a main line and a haul back line. The main line connects directly to the grapple mechanism and is used to move the grapple towards the crane and to close the grapple. The haul back line passes through the pulley on the back spar and then to the grapple and is used to move the grapple out, i.e. away from the crane. By adjusting the tension in the main line and the haul back line the sag in the lines is increased or descreased and the grapple can be raised or lowered.
The variations include the use of twin main lines wherein a second main line is used to open the grapple. In this arrangement each of the main lines uses an individually controlled winch having an on/off clutch connected to the drive and a controlled variable friction water cooled brake. When hauling the grapple in toward the crane brakes on these winches are released and the clutches engaged while tension is maintained by application of a hold back brake and the speed is regulated by the engine throttle. To haul the grapple out, these main clutches are disengaged and the main brakes applied to adjust line tension and thus the sag of the lines and at the same time the haul back clutch is engaged to activate the haul back winch to draw in the haul back line and move the grapple out, away from the crane. Opening and closing of the grapple is obtained by relative movement between the two main lines which are sometimes named as the opening and closing main lines.
In another form of machine, the opening main line is replaced by a smaller diameter tag line whose prime function is to open the grapple. The tag line winch is driven by a variable friction water cooled clutch to haul in the tag line or resist to it being pulled out thereby maintaining a tension in the tag line. The grapple is opened by increasing the tension in the tag line above that of the main line (by tag line clutch, main line clutch and/or brake manipulation).
The third variation incorporates two main lines driven at the same speed, one of which is designated an opening line, passes through a line shortener so that the opening line may be selectively shortened by operating the line shortener to thereby open the grapple.
All machines are provided with locking brakes normally air operated to lock all the winches for example, for parking.
The cab, boom, winches, drive, etc. of the crane are all mounted from a platform that is rotatable in opposite directions via a swing left or a swing right clutch driven by the main motor to swing the boom, cab, etc. to the left or right respectively.
The control systems currently available for this equipment require individual direct manual control of each of the various drive clutches or brakes and for the operator to selectively engage and/or disengage clutches and/or brakes to obtain the desired operation or direction of movement of the operating element or grapple. Thus in current machines such as a grapple yarder having a haul back cable drive, a closing main cable drive and an opening main cable drive, each with its own brakes and clutch, the operator is required to select and directly control each of the drives and each of the brakes independently and to adjust the throttle or power source to obtain the desired rate of change. For example to move a grapple in requires that the operator simultaneously activate both opening and closing drives (in tag machine only the closing drive is controlled) and disengage the opening and closing brakes, partially releasing the haul back brake to apply the desired drag to the haul back cable and adjust the throttle to obtain the desired rate of movement. In such a double main line grapple yarder, the operator, in manipulating the grapple, must coordinate the movement of three levers, two joysticks, three pedals and a knee control. Obviously this requires a significant amount of physical and mental effort sometimes very rapidly when transferring from one direction to another and to control the movement and operation of the grapple. Obviously excessive mental and physical effort leads to fatigue reducing the effectiveness of the operator. Also, to become a proficient operator takes a significant amount of training time.
Integrated computer operated controls have been used on a variety of different equipment however, prior to the present invention no integrated manual control system has successfully been applied to a cable operated machine such as a grapple yarder.